1. Field of the Invention:
This invention relates to vehicles capable of traversing rough terrain, and more particularly to vehicles having frame structures which are capable of moving relative to the body being supported when the vehicle encounters rough terrain.
2. Description of Prior Art:
Many vehicles are designed to traverse rough terrain. Some unevenness in the terrain is usually accommodated by providing a suspension system for each of the wheel assemblies, or other ground engaging members, to permit the wheel assemblies to move relative to the vehicle, which is normally provided with a rigid frame to which the suspension systems are attached.
However, even with conventional suspension assemblies, the wheel assemblies and frame may be subjected to excessive loading. Consider, for example, a vehicle having a conventional rigid frame, suspension system and four dual tire assemblies, one of the dual tire assemblies being positioned at each of the corners of the vehicle. If one of the tires of the assembly passes over a large rock or the like, the wheel will rise causing the entire weight normally borne by both tires to be borne by only one of the tires, and then only on the area which is in engagement with the rock. The tires must thus be designed to absorb these anticipated loads, which, obviously, far exceed the normal operating loads.
If, for example, both tires of one of the dual assemblies encounters a very high spot then the opposite dual assembly may be lifted significantly or completely clear of the ground. In this instance the dual assembly in engagement with the ground will support up to twice its normal load, and the tires must be designed accordingly.
Further, if large irregularities are encountered, the limits of the suspension systems may be reached. Loads transmitted through the suspension systems must be absorbed by the vehicle and generate stresses in the frame. The frame therefore must be designed to absorb dynamic loading far in excess of normal loading. Thus, with vehicles employing pneumatically inflated tires, the tires must be designed to withstand loads which greatly exceed the normal operating load, and frame structures must likewise be designed to accommodate stresses which greatly exceed the normal stresses which will exist in the frames when the suspension systems are operating within limits.
Thus, the tires and frame assemblies must be designed to accommodate loading which greatly exceeds the normal loading, and the cost and size of both of these components could be reduced if it were not necessary to design for greater than normal loading when rough terrain is to be encountered by the vehicle.